1. Field of the Invention
The present invention relates to an in-vivo information acquiring system provided with an in-vivo information acquiring apparatus introduced into an object to be examined and an external signal generating apparatus disposed outside the in-vivo information acquiring apparatus to operate the in-vivo information acquiring apparatus.
2. Description of the Related Art
In recent years, swallow capsule type endoscopes are making their debuts in the field of endoscopes. A capsule endoscope is introduced into a body by being swallowed from an examinee's mouth and moves inside the body cavity, for example, organs such as stomach or small intestine according to peristaltic movement and picks up images one by one until the capsule endoscope is spontaneously discharged.
Image data picked up in the body by the capsule endoscope while the capsule endoscope moves through the body cavity are transmitted one by one to the outside through wireless communication and stored in a memory provided in an outside receiver. After swallowing the capsule endoscope, a patient can freely act by carrying the receiver until the capsule endoscope is discharged.
The capsule endoscope obtains drive power from a battery or the like which is built in a casing, but since the capsule endoscope has a structure with an inner circuit or the like hermetically sealed in the casing, a user cannot perform ON/OFF operation to drive the endoscope by operating a switch or the like disposed on the outer surface of the casing. Thus, a capsule endoscope system is proposed which is provided with a reed switch short-circuited/released by an outside magnetic field in the casing of a capsule endoscope and a permanent magnet in a package in which the capsule endoscope is accommodated and held. The reed switch is structured so as to maintain a released state in an environment in which an outside magnetic field of predetermined intensity or more is given and be short-circuited when the intensity of the outside magnetic field decreases.
Therefore, when the capsule endoscope is accommodated in the package provided with the permanent magnet, the capsule endoscope does not operate before use, but starts to operate when the capsule endoscope is taken out of the package and is not affected by the permanent magnet. This allows the capsule endoscope to prevent battery consumption before the start of use.
Furthermore, a capsule endoscope disclosed by the present applicant in Japanese Patent Publication No. 4139296 turns ON/OFF a power supply from a battery to function executing sections such as an image pickup section through a toggle operation in response to an external signal such as a magnetic field. Thus, the user can perform ON/OFF operation on the capsule endoscope through an external signal even after taking the capsule endoscope out of the package.
Here, the switch may be repeatedly short-circuited/released in a short time due to chattering of the switch operated by the user to generate an external signal, misoperation by the user, or the like. The interval of the toggle operation is then shortened.
However, a measure should be taken for the capsule endoscope to prevent the interval of the toggle operation from becoming short to secure a time necessary to reset an inner circuit.
In order to solve this problem, the present applicant discloses a capsule endoscope 110 shown in FIG. 1 in Japanese Patent Application Laid-Open Publication No. 2008-12036. In addition to a reed switch 135 that turns ON/OFF according to intensity of a DC magnetic field, the capsule endoscope 110 includes a mask signal generation circuit 123 for masking a switch signal Vin from the reed switch 135 for a predetermined period.
When the reed switch 135 is OFF, the switch signal Vin is at a power supply voltage level, and therefore a P-MOS transistor 144 turns OFF and an N-MOS transistor 145 turns ON. A charge stored in a capacitor 147 is then gradually discharged according to a time constant determined by a resistor 146 and the capacitor 147 and a signal Vmask is outputted. On the other hand, when the reed switch 135 is ON, the signal Vin at a ground voltage level is outputted, and therefore the P-MOS transistor 144 turns ON and the N-MOS transistor 145 turns OFF. The capacitor 147 is then charged and the signal Vmask is outputted as a power supply voltage level.
Here, an inverter 141 outputs a signal Vout1 which changes from a ground voltage level to a power supply voltage level when the value of the signal Vmask falls to or below a predetermined value Vth. When charging/discharging of the capacitor 147 is repeated and the signal Vmask does not fall to or below Vth, a mask period is formed during which even if the signal Vin changes, the change is not transmitted.
Here, the signal Vout1 is inputted to an inverter 142 and the inverter 142 outputs a signal Vout2 which is obtained by inverting the inputted signal Vout1 to a divide-by-2 frequency-dividing circuit 143. The divide-by-2 frequency-dividing circuit 143 divides the inputted signal Vout2 by 2 as an ON/OFF control signal Vout and applies Vout to a gate of a power supply switch 114. Since the power supply switch 114 is a P-MOS transistor, the power supply switch 114 turns ON when Vout is at a ground voltage level.
Since the capsule endoscope 110 has the mask signal generation circuit 123 using a charging/discharging circuit, even if the intensity of the magnetic field from the outside magnetic field generating section is unstable, the interval of toggle operation is never shortened.